Messages in this thread | | | Date | Wed, 23 Nov 2011 19:10:18 -0500 (EST) | Subject | Re: [PATCH] qlge: fix size of external list for TX address descriptors | From | David Miller <> |
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From: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com> Date: Wed, 23 Nov 2011 21:10:42 -0200
> When transmiting a fragmented skb, qlge fills a descriptor with the > fragment addresses, after DMA-mapping them. If there are more than eight > fragments, it will use the eighth descriptor as a pointer to an external > list. After mapping this external list, called OAL to a structure > containing more descriptors, it fills it with the extra fragments. > > However, considering that systems with pages larger than 8KiB would have > less than 8 fragments, which was true before commit a715dea3c8e, it > defined a macro for the OAL size as 0 in those cases. > > Now, if a skb with more than 8 fragments (counting skb->data as one > fragment), this would start overwriting the list of addresses already > mapped and would make the driver fail to properly unmap the right > addresses on architectures with pages larger than 8KiB. > > Besides that, the list of mappings was one size too small, since it must > have a mapping for the maxinum number of skb fragments plus one for > skb->data and another for the OAL. So, even on architectures with page > sizes 4KiB and 8KiB, a skb with the maximum number of fragments would > make the driver overwrite its counter for the number of mappings, which, > again, would make it fail to unmap the mapped DMA addresses. > > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Applied, thanks for the detailed commit message.
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